I have long experience with Li batteries used in model airplanes,
BE VERY VERY SURE your replacements
have the same chemistry as the original.
They are most likely Li-Ion in SS cases
I've used China
batts in my ICOM radios getting them to fit is the hardest part. also they seem to be much lower quality than original.
But a new Rx would be a better way to go at L99 ($120?)
I bought a new hand held that floats for $99 at West Marine last year, very handy.