Lee Sir,
Recommended budget bipods for the Zastava M77:
1. UTG Recon Flex M-LOK Bipod
Best for: M-LOK handguard owners. This bipod attaches directly to the 3 and 9 o'clock positions on M-LOK handguards without needing a separate adapter. It's made from aircraft-grade aluminum, has 5 Posi-lock leg positions, and features spring-loaded legs for quick deployment. If your M77 has a factory-style wooden handguard, you will need to swap it for an M-LOK compatible one.
Price: Around $75.
2. CVLIFE 6-9 Inch Bipod
is for budget-conscious shooters with a Picatinny rail. The bipod includes a Picatinny adapter and offers good performance for the price. This bipod is made of hardened steel and aluminum, is equipped with a non-rust black anodized finish, and has adjustable legs with spring return. To attach, you'll need to install a Picatinny rail section on your rifle's handguard.
Price: Around $22.
3. Caldwell Accumax Pivot Bipod
Best adjustable bipod for use on uneven terrain. The Caldwell Accumax offers both pan and cant features. This bipod is lightweight, offers a 180-degree leg angle adjustment, and allows for 360-degree swivel rotation and 10-degree cant.
Attachment: The sling swivel stud model can attach to a stud installed on a traditional handguard. The M-LOK version requires an M-LOK handguard.
Price: Around $94 for the M-LOK version or $100 for the carbon fiber sling swivel stud model.
Hope the above information helps Sir Lee, please take care and stay safe 🙏

I would def go with the Caldwell Accumax Pivot Bipod that’s good on even and uneven terrain and priced less than $100. The Caldwell Accumax is lightweight, offers a 180-degree leg angle adjustment, and allows for 360-degree swivel rotation and 10-degree cant. The sling swivel stud model can attach to a stud installed on a traditional handguard.