The only real challenge is going to be making a secure lid for it. The simplest way to do it would be to find a local shop with a CNC machine to cut a piece of acrylic to size, but that won't be cheap.
You could get some hardware cloth from home depot and cut them to fit. Then the issue becomes how to secure it to the tank. You might be able to find a shop that can bend some pieces of aluminum or stainless to fit the curvature, but once again that could be costly.
Plastic light diffuser grates also available at home depot could be cut to fit and if there is a big enough ledge in the trim of the top of the tank it could sit in place and just have something heavy placed on it to keep it secure. The only down side to this is that any reptile kept in the cage needs to be big enough that it couldn't escape.
If I were given this cage I would use it for something that didn't need a lid. Maybe a leopard gecko? Honestly I would use it for fish lol.