The 210 will probably be your best bet, so many of them made they are cheaper than others, IMHO. True the opening size on the lens board dictates what lens/shutter, so check first.
You may want to play with the idea of black tape and a copper or foil sheet and make a pin hole in it and then tape it to the center of your lensboard. Pinhole photography might be a fun cheap start, till you achieve your lens. Read up first.
You may also want to cut down printing paper and do paper negs too, to hold down your film expenses until you have a real lens while shooting pinhole... long exposures !!!!! Again, Read Up.