Fox cool, they have... hatch rear shock hole covers now..

[kendawg73]

Mustang Hatchback Shock Access Hole Covers (90-93) - LMR

Pick up these 5.0 Resto direct replacement 1990-93 Mustang shock access hole covers, to replace your old and worn out covers in your Fox Body hatchback!

lmr.com

 

[Mstng93SSP]

And the price is actually very reasonable.

 

[Mustang5L5]

Finally, after I spent months looking for a set at a reasonable cost on eBay.