@Craig T Vector
I bought my hard case for the T-40 from an Australian company called Swamp Industries for approx $100AUD. It fits perfectly too. The info is below but the shipping cost would be prohibitive most likely..have a look anyway. You may find a similar seller in the USA. The case dimensions are below..I measured the bass first and queried Swamp Ind. as to the case size and they included the dimensions..so yes the T-40 fit well.
BASS GUITAR HARD CASE - ABS STYLE
RS-BC-501
SWAMP Bass Guitar Hard Case - ABS Style
View attachment 4363641
I left this review on their website...
"As is known in the world of bass guitars, the Peavey T-40 bass guitar is one of the heaviest 4 string basses ever made. The width of the bottom half of the body is quite wide and requires a case to suit it's dimensions. As these vintage basses were produced between 1978-1987 and are quite old, you will often find them for sale without their original cases. My 1979 T-40 fits nicely inside one of these Swamp ABS style 5 string hard bass guitar cases. If the bass guitar was 1" longer or wider it would not have fit, but sits snugly inside the Swamp case. The case is very well made with plush interior, solid construction, excellent hinges, 4 good catches (1 lockable with keys) and a good sturdy handle. The exterior cases ribbing on front and rear gives the case a firm solid feel and the newer styled RS-BC-501 case with it's aluminium edging on both body and lid gives it a modern sleek look. Overall it is a solid, well built bass guitar case, made for large 5 string basses or in my situation it suits my wide beam 4 string 1979 Peavey T-40 bass guitar. Good valued case for around the $100 mark. Thanks Swamp. 5 Stars. Giff."