You might get moderately close with whatever Eminence tells you, and for a single driver out of 8 it might not make much difference in sound (maybe mount the new different one on the bottom row if you do that). Personally, I would want to find a replacement from that same cab in the wild, but it might take some time. I'm not sure how similar they are to the other "Working" 10" based cabs, since that's the Rocco Prestia signature cab (hence the "Tower" name). Since it's an 8 ohm speaker you might get lucky (as opposed to a 32 ohm which would mean only another 8x10 would have them, most likely, and that was the only Working series 8x10 they made). I would also assume that even a "similar" driver from another Working cab would be closer in specs and sound than an off the shelf Eminence. Eminence will definitely try to sell you a new driver because they don't make any money if you go on ebay and reverb and get something used.
But if you find out that say a 4 ohm Workingman's (or WorkingPro, whatever) 2x10 has similar or even identical drivers, you could snag one of those for probably cheap (I would guess 200 or less), take out the driver you need, keep the other as a spare (or put it in the cab in the same row as the other one and use the good driver you take as the spare), and then find 2 suitable replacements for the Working cab and re-sell it as such, or just sell it empty for someone to do that themselves. That might not be the CHEAPEST method, but I believe it would yield the best results.
But if you find out that say a 4 ohm Workingman's (or WorkingPro, whatever) 2x10 has similar or even identical drivers, you could snag one of those for probably cheap (I would guess 200 or less), take out the driver you need, keep the other as a spare (or put it in the cab in the same row as the other one and use the good driver you take as the spare), and then find 2 suitable replacements for the Working cab and re-sell it as such, or just sell it empty for someone to do that themselves. That might not be the CHEAPEST method, but I believe it would yield the best results.