Excellent score! Glad you finally got one. The 21 is the VHF model, the 41 is the UHF, and the UHF is what they used. AFAIK, externally, the only difference is the model number labeling, which doesn't really show clearly on screen anyway. You'll need the shorter UHF antenna and you're set. Looks like you've got the standard battery pack which should be correct. I'm still looking for the antenna and standard pack for mine since it came with the larger high-capacity pack. Next time I go up to R&L Electronics I'll see if they've got any of the UHF antennas in their used parts section. And the Dayton Hamvention is just a month away too.
Jim