Now that we have all the major and important components covered, we’re getting to the end of the list of lesser important things. If you’re not careful with choosing these things, your bike still probably still run quite well, but then you’ll have to pay your LBS to get them, and spend too much money on things.
Headset spacers (#4 on the Parts List) go between the headset bearings and the stem (see the picture on the right if you don’t already know what they are). They can be made of alloy or carbon or plastic. There isn’t a large difference in cost, but since you’re building up a carbon bike, you might as well get carbon spacers. The best place to buy headset spacers is on eBay, but expect to wait 1 to 2 weeks for delivery by standard mail if you live in North America. You shouldn’t spend more than $3 to $5 USD, although prices on eBay do fluctuate. Most carbon forks on road bikes require 1⅛” spacers (there are 1″ spacers also on eBay, that’s probably not what you want) but you should first check with the specs of your frameset. On the left is an example from a recent listing (Nov. 2014) on eBay. I captured the screen shot using my phone. This set is unusually cheap, so don’t expect to always have this kind of a deal. The point is that it comes with 4 spacers of different lengths. You almost certainly won’t need all of them, so save the extras for a later project…or be evil and sell them to a friend at a mark-up. This should convince you not to buy the heavier and less-cool-looking plastic spacers. I am, however, short of telling you not to get alloy spacers. The advantage of an alloy spacer is that they can come in different colours, which can add a personal touch to your bike.
Tip: Buy a set that comes with different lengths. That way, once you have figured out the height of the stem, it’s easier to make fine adjustments.
When you build up your bike, you’ll need to have cables and housing (#22 on the Parts List). Shifter cables are usually included in the groupset, but not brake cables, and cable housing is never included. There is a Taiwanese brand called Jagwire; you’ll find a lot of brand-name bikes using their cable housing too. A very basic set of Jagwire housing kit sells on eBay for $7-$10 USD, and that’s the cheapest place you’ll find them. As you can see from the listing on the right (from Nov 2014), the kit can be in all sorts of colours depending on your personal preference. But of course you can always pay more for a higher-end kit. (I have to watch my spending, so I have never been able to splurge and buy those. If you have experience with them let me know.) Just as a word of caution, when you build up your bike, you’ll have to cut the cables and the housing to their appropriate lengths. Make sure you have some strong cable cutters for that job, or you will end up paying extra for your LBS to do that for you.
A lot of carbon frames now have internal cable routing, so it’s sometimes best to have two inline cable adjusters (#23 on the Parts List) for the shifter cables. This is so that you can make adjustments on your derailleur on the fly (while you’re riding) if the shifting alignment is off. If your shifter already comes with cable tension adjusters (Shimano Tiagra comes to mind), you may not need it at all. But if you do, they cost around $10 USD, and they come in all sorts of designs and colours. Again, the best place to buy them is on eBay, but expect to wait 1-2 weeks for delivery by mail if you live in North America.
About the most unimportant “little piece” is the water bottle cage (#22 on the Parts List), and that’s why I have it at the very last. Yes, like everything I’ve said before, the best place to buy carbon water bottle cages is on eBay. Expect to pay about $20 for two carbon cages, although you may have to wait awhile to get a good deal. I use cheaper alloy cages myself, because I have a habit of breaking the carbon cages that I had. I’m sure it’s my fault for the way that I pull my bottles off the side, but I have sworn off carbon fibre cages for now. If you’re looking at the alloy alternative anyway, and if you’re in Canada, Mountain Equipment Co-op sell them for about ~$5 CAD each.