Welcome back to the hobby and much has changed while you were away. First off if your 72 Tx is in good working order and is a modular unit you can easily switch it to 2.4 by using a FrSky module, which is a straight plug and play affair. Their systems have been proven to be bullet proof and cost a fraction of what other leading brands cost while giving outstanding performance.
Regarding Tx batteries, for some time now I have been using Life 3S 2000 mA battery from Hobby King in my Futaba 8UAF Tx which I upgraded to 2.4 with a FrSky module and to date have been quite pleased with it's performance. If you however like many others feel uneasy using a HK product check with Richard at Wrong Way R/C and he will be able to give you good advice and also provide you with whatever battery etc. you might need.
Last edited by karolh; 04-05-2019 at 04:24 PM.