Steve,
Just about any dual reservoir Ford chrome cover will fit....Below is one that I bought..Only a few bucks.
http://cgi.ebay.com/ebaymotors/Chrome-Master-Cylinder-Cover-Brakes-Ford-Mustang-Tbird_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1171Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a0Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem5ad0c6f28aQQitemZ390049755786QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
BUT, and isn't there always a BUT!!!!
The BUT in this case is the RUBBER SEAL between the COVER and the MASTER CYLINDER....When you purchase the typical CHROME COVER, it DOESN'T come with a RUBBER SEAL...You might be lucky and can reuse the old seal..In my particular case, I wanted to replace the RUBBER SEAL so I took my EBAY CHROME COVER to NAPA and they found one to fit.
Come on now, did you really think that changing something on a Shay was going to be easy?????
Oh, before I forget, someone a while back mentioned that the MASTER CYLINDER used on Shay's was a GENERAL MOTORS BUICK part and I cannot prove or disprove this BUT, there's that word again, I went on EBAY and bought a CHROME COVER to fit a 1979 Ford MASTER CYLINDER and it fit.
Reggie