Due to my poor charging habits in the past, I'm down to one functioning Tx battery (and three functioning radios). I'm using Airtronics radios with the old 8-cell "square pack" and for some reason it seems next to impossible to find spar batteries from Airtronics/Sanwa. I've even thought about buying another RDS8000 just to get the battery and the receiver (which together count for half the cost of the radio). But the packs supplied with the radios are only 700mAh.

I wasn't able to find a suitable Tx battery from Tower, but a quick google search turned up this battery on Amazon:

http://www.amazon.com/Tenergy-2000mA.../dp/B00384JI3K

SR Batteries offers 8-cell square pack but they seem awfully pricey at about $70 (plus shipping).