God gave you judgement and wisdom.
Please use it to determine that there is a reason that company is out of business.
There is also a reason your unit broke with people on it.

Check with your premises liability carrier to determine the wisdom of fixing a unit that should probably be removed.

Maybe a ramp would be better or possibly a movable wheel chair lift. These things are an attractive nuisance for children to play on or around and get hurt. If your church is renting the building, check with the building owner for paying for its replacement.

A church member who is a machinist can make almost any part, but will your insurance carrier cover you in case of another such accident? You have knowledge that the product is obviously defective.

I suppose in your current situation, you will have to make an alternative reasonable means to access where ever its going or face an ADA law suit. Balance that against a negligence premises law suit where it can be proven that your conveyance was not properly maintained.