First, find out about cell phone coverage in the area you'll be in. Out here in the west, there are vast areas with no coverage--I often lose coverage quite a while before I reach the trailhead on the way in. However, I understand that back east there are very few areas that don't have coverage at least for texting even if not for talking. It might be that your cell phone is sufficient.

When I googled there was a McMurdo Fastfind listed in the upper $200's. I didn't check to see if the firm had it in stock. I strongly suspect that one of the newer small ACR units would be better. My Fastfind was the latest and greatest 2 1/2 years ago, but in terms of electronic devices, that's almost ancient history!