Yup... those are cool and really useful, You can get the slip in bushings from theyardstore.com or browntool.com for a decent price, they require a drill block or an egg cup bushing holder or with the smaller sized ones you can just use them upside down. These can be bought one at a time or in kits.
this is the egg cup type bushing holder and a set of screw in type bushings, these are very useful and you can hold them upside down when space is limited, They also have the slip in type and drill blocks... LOTS of different stuff just by searching "drill bushing at this site. http://www.yardstore.com/browse.cfm/4,6385.html
Also a really good place to get carbide rotary files on the cheap in either the 1/4" or 1/8" shank size, I got a few extra long 1/8" ones about 10 years ago or so and they'll get into the transfer openings really easy.
Other stuff that's highly recommended from these sites is a set of Cobalt drill bits, they'll outlast High speed steel bits several times over, pancake adapters fro drilling in tight or really awkward places when disassembly is just not convenient or will take a lot more time than necessary. Reamers are also nice to have when you need a perfectly round and clean hole and tolerances are too critical for drilling, and an assortment of clecos for temporary assembly or holding parts together to speed up assembly and disassembly when doing jobs where a part needs to be installed and removed several times before the final assembly... These make excellent "third hands" for a lot of small projects and especially when sheet metal or fiberglass, or plexiglass is involved.