Rental reimbursement cap is $30/day - it's been 6 weeks and my car still isn't fixed. What are my options?

Got rear-ended six weeks ago. Total liability claim against the other driver's insurance (Geico). The other driver was 100% at fault - no dispute on that. My car has been at the body shop for almost the entire time because of parts delays. Shop says it's an overseas part that keeps getting pushed back.

The problem is my own policy has a rental limit of $30 per day up to 30 days. I'm now past 30 days and the cheapest rental I can find around here is $52/day. I've been paying out of pocket for the overage and now I'm past the 30 day cap entirely so it's 100% out of pocket. Over $700 out of pocket now and growing.

I know the other driver's Geico policy covers my rental through their liability coverage and there's no cap the same way my own policy has one. But Geico keeps saying they'll only cover "reasonable" rental costs and have capped me at $30 as well even though that's not from my policy. Can they actually do that? The repair delay is their insured's fault - I shouldn't be eating this cost.