Before springing for a chronometric I put a bicycle speedometer on my A10. The model I got from Cateye was a Velo 5, now discontinued, but still on the bike along with the chronometric. Properly calibrated according to wheel diameter, I believe the Cateye is quite accurate and it closely matches the chronometric. You can get the Cateye brand (and, I'm sure) many others, wired or wireless. A Cateye Velo 7 (wired, for up to 125 MPH) would set you back around US $30.
I eventually bought a rebuildable chronometric because I think having working history is a big part of what's cool about the bike. Be sure you don't give up on your chronometric. If you do your own work on the mechanics of the bike, you might be able to deal with the repair and cleanup of the speedo. There are some pictures of speedo guts here on the forum. Let us know if you want to be steered to them.
Richard L.