Stainless gas struts are fairly cheap
in uk and I suspect in US. If you have a working one use a spring balance or hand held luggage scales to measure the force needed to start compressing it. Then measure closed and open length and end fittings. The spec may be engraved on the old one.
If you have not got a working one, either measure the force required to hold the top open using luggage scales etc and then use fairly simple mechanics to calc strut force required, and then add a bit more to positively hold it open. Or, you can buy gas struts which you can adjust their load capacity downwards once fitted.
Used them on my FP Maldives
which had a pop top and intend using them on the FP Athena fridge lid and engine
/bunk boards to service
the engines without dismantling the stern berths.
Last time I looked they were about £30 a pop so should be $30US.