If you visit HIS Glassworks, they have free plans for making your own lap wheel, and it's relatively inexpensive (of course, the diamond discs are NOT...but you can also built a grit wheel that uses silicon carbide and is much cheaper).
My favorite sources for cheap coldworking stuff are (in order): Online, lapidary stores, dental supply places and stone masons. Frequently I can pick stuff up in those places, used, for less than I could fabricate it myself.
Online, start with craigslist and ebay (be careful with ebay, especially if the equipment has to be shipped, which can wipe out your savings). Many glass coldworking supply places online will have a "used" section, although stuff goes pretty fast. In lapidary stores, make sure you visit in the first quarter of the year--that's when people get rockhound stuff for Christmas or Valentines, use it two or three times and get bored with it.
Dental supply houses will carry stuff to blast grit and cerium out of bubble holes, small tools for poking sandpaper and grit into details, water delivery systems, etc. And stone masons (or stone carving supply houses) use exactly the tools we do, but often better-priced and sometimes used.
The big thing is to be patient, visit these places fairly often and work up a relationship with the store owner so that he knows what kinds of things you want. In a couple of cases owners have accepted used equipment on consignment figuring that I (or a glasspal I knew) would buy it, when otherwise they would have turned it down.
And keep an open mind--just because it's not a Merkur lathe doesn't mean you can't make it do many of the same things with a little modification.