If you want film holders, try mpex.com or look on eBay. For 2x3 sheet film, try J&C.
About mounting a roll holder, the trick that Jo Lommen published is well-known -- Graflex, Inc., sold a kit to accomplish the same thing -- and prevents focusing on the ground glass. If you're going to shoot only with the 101/4.5 Optar and focus using the Kalart, the trick will do just fine for you. Note that the Kalart's close focusing limit is around 3 feet.
If you want to focus on GG, then your best option is the despised Adapt-A-Roll 620. Read about it at www.graflex.org. Oh, and by the way, I wrote the FAQ on it there.
Or sell the Busch and get a Graphic with a Graflok back. The Busch is slightly more capable but, IMO, less useful than a 2x3 Pacemaker Graphic because splicing a Graflok on one is a major job and because boards for the Busch are very hard to find. Nice camera, its a pity they are so poorly supported.
Good luck, have fun,