The following was submitted by Peter Ashby, and is a welcome contribution to the world of budget astronomy.
For me the cheapest and best finder that you can have on a scope is a homemade one, an old pair of cheap 10x50 binoculars (got at a junk shop, boot sale or charity shop) can make two excellent finders, here in the uk the cheapest I have paid for an old broken pair was £1 (one of the objectives was chipped so useless).
I dissassemble the whole thing and use a thick walled cardboard tube to mount the objective, a second length of tube is split and a section removed down its length such that it will fit inside the first tube and slide. using the fitting that the eyepiece slides into (usually screwed to the body of the binoculars, you make a hole in the smaller tube and screw this part into it. for a diagonal use one of the prisms, cut a piece of wood that fits into the smaller tube with a 45 degree cut and fix the prism to this. then all that is required is the correct positioning of the prism to reflect the image up the eyepiece holder, put in the eyepiece part (a bit of sticky tape will stop it falling out if needs be)and then slide the inner tube into the outer until you get focus. Cross hairs can be added by superglueing a couple of human hairs across the back end of the eyepiece.
A later version I have made used a small (17mm) f/s mirror mounted to the diagonal face of the prism as the diagonal. To get alignment either mount the whole thing on a fairly flexible aluminium bracket and bend the bracket to align, or as I have done on one of mine find a cardboard tube slightly bigger in diameter and mount the finder in this using 6 screws just threaded through the cardboard. a coat of varnish or paint on the whole thing makes it reasonably dew proof for my scopes that only go out when I am observing.
Peter Ashby (aka Grendel)
aescinga AT pgen DOT net