Actually, I think the best solution is to buy the empty battery tray for the FT-60. Then buy some Eneloops or equivalent AA-sized NiMH batteries--you will need six per set.
Costco is where I've bought my battery sets--they typically have AA's and AAA's; a four cell charger; and may have adapters to use the AA's as C's or D's! They hold their charge for an extremely long time and are high capacity.
For convenience, you might want to buy two sets so that you get enough charger space to charge all six cells at once. I also use these for my camera flash, so I have three sets: Plenty of cells; two chargers for the FT-60R; and one more charger for my camera bag. All of that provides plenty of cells for two sets of six for the radio and two sets of four for the photography plus extras for other uses (such as small flashlights).
Hope you find that useful.
73,
JERRY, N3AA