Does your 99 have the stitch length lever?
A brand new wooden base is rather costly at least the nice ones. A guess a used 99 in a bent wood case or suit case type is the most reasonable price. The original cases were high quality and did cost quite a bit when they were new. Depending a bit upon use and storage, the new ones can have nice features like
this one. I assume people are willing to pay a bit to equip their favorite machine. There
are tutorials on how to make one if you ever get the chance. SewClassic seems to have only for
full size machines, simpler, but at a much lower price. For a better price you need to search a bit.