Much of the information and a number of images related to merchandise were furnished by Kevin Leahy. Thanks, Kevin!
AnimeNation will special-order most of the VHD novels and a number of other related books. They sometimes stock VHD merchandise also.
Animate USA. (On hiatus as of June 2004.)
House of Anime. Some merchandise is not licensed (i.e., bootleg).
For books, another good source is Sasuga Japanese Bookstore, where you can order many titles through the web. I have also had favorable reports of Kinokuniya. If you can read Japanese, check out Amazon Japan.
Some other sources of merchandise are listed with merchandise descriptions. I will add links to sources as I learn about them.
Bidding services:
Shop around and compare to see which fits your needs best. At the moment, Rinkya is the only service that allows viewing of completed auctions: paste in the URL at http://www.rinkya.com/finished.html.
You can use these links to search Yahoo Japan auctions for the phrases kyuuketsuki hantaa D, banpaia hantaa D, vanpaia hantaa D, banpaiya hantaa D, vanpaiya hantaa D, Hantaa D, and Amano Yoshitaka. Searches for "Vampire Hunter D" on bidding services may give different results.