That gasket is readily available as are most the engine gaskets.
BEST Gasket is the company that makes them. There are 2 gasket in that area. time Timing cover gasket (RED) which goes behind the timing cover and is easier to change/replace just have to remove the crank pulley . the second is the Timing Cover Plate Gasket (CYAN), which goes between the mounting plate and the engine block, plate is right behind the timing gear & crank gear it has screws that hold it to the block, it is the plate that the timing cover secures to.!! it is more work as you have to remove the crank & timing gear.
The Timing Cover Gasket is 11019E
Basic Listing is here, and on their site:
Chevrolet
6-cyl
1929-31 Master 194.......[501]
DESCRIPTIONPART NO.
ENGINE REBUILDING SET.................RS501C
HEAD GASKET....................................501C
INTAKE & EXHAUST MANIFOLD SET.....12004
OIL PAN SET.....................................26002
PUSH ROD/VALLEY COVER SET..........25020E
TIMING COVER GASKET....................11019E
TIMING COVER PLATE GASKET...........10013E
VALVE COVER SET............................25005E
as where to get them:
Try the Usual Suspects*
The Filling Station in Oregon
.....Website:
The Filling Station.....Phone:(800) 841-6622
*
Gary Wallace in Missouri
.....Website:
Early Chevrolet Parts.....Phone:(314) 293-1991
*
Lonny Ekstrand in Texas
.....Website:
Stanleys Parts.....Phone:(817) 478-7265
*
Bob Marx in Wisconsin (Posts on here as marxparts)
.....Website:
Marx Parts LLC: Antique and Vintage Car Parts.....Phone:(715) 652-2405
also for Gaskets:
*
Olson Gaskets in Washington
.....Website:
Olson Gaskets.....Phone:(360) 871-1207