The original TNR15G221K is made by Nippon-Chemicon, the V130LA20AP (very common replacement) is made by Littelfuse. The Littelfuse part is better.
I have the Littelfuse part here:
https://www.greatplainselectronics.com/proddetail.asp?prod=V130LA20AP
I'm sure the other parts sellers in this forum also carry equivalent parts.
They are both rated at same varistor and max voltages:
TNR has "221" in part number which is 'varistor voltage', Littelfuse has "130" in the part number which is 'maximum continuous voltage'. If you compare varistor voltages and continuous voltages to each other - they are the same. That difference in numbers just adds to the confusion factor.
The real difference between the two is Littelfuse part is a 20mm diameter part, Nippon-Chemicon part is 15mm diameter.
That extra 5mm difference will provide a bit of extra protection because the "clamping current" is considerably higher for the bigger part (6500A versus 4500A). This clamping current is a sudden surge of current due to 'clamping' or cutting off excessive voltage spikes.
Note -- the TNR15G221K has been discontinued by Nippon-Chemicon. Their replacement is a TNR14V221K. Smaller diameter part but thicker than original. Closer but still lower clamping current rating than Littelfuse.
I carry the Littelfuse part as found here:
https://www.greatplainselectronics.com/proddetail.asp?prod=V130LA20AP
Can also find a better Corcom (Tyco) filter here:
https://www.greatplainselectronics.com/proddetail.asp?prod=5VB1
But it is pretty rare for the filter to fail.
I'm sure the other parts sellers on this forum have them as well.