Find an old pair of binoculars and take the large end off. There is usually a narrow throat that serves as an aperture engineered into the case and the whole thing screws off together. They make great portrait lenses and you get two for the price of one! The attached shot of our own bill h was shot with a Speed and the objective lens from an old set of 7x35 Crown Optics binoculars.
Thanks for all the answers everyone. I found an old 9x12 folder camera (that I guess technically was my first "LF" camera) and took the lens from it, it's even got a shutter. The original lens was a 135mm, but after unscrewing the rear element it seemed to become something significantly longer (probably around the 200m) mark. I haven't been able to test it properly since I lack a lens board of the correct size, but I was able to sort of keep it in place on a larger lens board and observe the image on the ground glass.
You don't say which Speed you have but if it's an Anniversary or earlier, lens boards are easy to make up from any number of materials. My favorite is masonite, but foam-core board in black has served me well on a number of occasions. Just cut them 4x4 and chamfer the bottom edge on the back so as to fit into the slot more easily. Draw lines from corner to corner to mark the center and cut out the hole to size. Usually talkes me about 15 minutes to make a "Q&D" board (quick and dirty construction).
I've used the foam-core board for lensboards as well, worked just fine for a couple of different lenses and is very lightweight to boot.
New Pacemaker boards are very cheap new from Heavystar in Ebay, it's worth buying three.
A piece of 1/4 inch black acrylic cut to the OD of a pacemaker board opening, corners rounded to fit into the opening, back sides routed down so that the center portion just fits into the bellows throat and the front edge just under the board locks ( approximately 1/16 inch thick lip ), back side sanded so that it has a flat finish, and center drilled to the shutter mount makes a very nice lens board that is very rigid. It is a little more work than foam core and the center portion going into the bellows opening eliminates the need for the outer lip light trap.