My rear derailleur has recently snapped off. The derailleur was a Shimano STX (RD-MC34) 7speed, and I would like to know what a good replacement would be. the bike will be used for mainly cross country with lots of climbing. would like to upgrade the drive train soon but not atm(cant afford too) so if there’s something out there that good quality that can handle(7speed for sure, and maybe 8 or 9 too) pls let me know.