Long term solution is to add insulation / figure out why that room is so warm. Do you have central AC now? If so, there might be something wrong with the duct supplying that room. Loose fitting, hole in supply pipe, etc. Or it could be an undersized supply. If its undersized your best bet is add insulation. Is there an attic above? Unfortunately I have found very few HVAC contractors that really know how to design/balance a system. The one I used when I built my "better than energystar" house is out of Annapolis and you are probably out of their service range.
Short term your best bet is the portable AC units with the two tubes that go into the window opening. If you want to save some $ try FB marketplace (now is probably not the time, fall/winter is best to find deals). I have no answer to the breaking within 2 years other than small appliances are a crap shoot these days. Ive had some break quick and others last.
Last option would be to install a dedicated mini split unit for that room. It will be a big upfront cost but should last 10+ years and are very quiet. Again, I would think the insulation / duct troubleshooting would be cheapest/best.
MRCOOL DIY 12,000 BTU 1-Ton 1-Zone 22 SEER Ductless Mini-Split AC and Heat Pump with 12K & 25ft Line DIY-12-HP-115C25 - The Home Depot
BTW those used to be like $500 before covid..