I am not familiar with all Tristar models, but the Turkish manufacturer of that brand usually has separate left and right-hand trigger groups for pumps and autos. So to reverse the safety, you must either replace the whole trigger group or disassemble and replace all the relevant parts of the OEM trigger, which costs roughly a third of what you paid for the gun.
I don’t know specifically about that model, but if you can look up an owner’s manual online, it will tell you. If it says the safety is non-reversible, they really mean it per above.
A call to a gunsmith might produce more info and you may be able to find instructions for DIY fix, but I would caution against following this course unless you really, really know what you are doing.
Grouse