Some of these places may be able to help. You might want to check the Kit Finds page to see if the kit you're searching for has been spotted by someone already. Check their web site for availability and ordering information. They also carry books, slides, videos, etc. relating to spaceflight and astronomy.
Service is quite good and reliable.
Best way to get the kits is to call them as soon as you receive the list. Even then, the kit you want may be gone. This is where I got my Revell Space Station kit. He also deals old kits, with prices around the CVG range. Again, good service here.