The TopFire looks like another relabeled FlySky radio.
There are two versions -- V1 has a main receiver plus a smaller satellite and V2 just has the single receiver with an antenna that has a lump near the end.
The two types are not compatible so you'd need to know if his is V1 or V2.
It's getting pretty hard to find V1 receivers now but HobbyKing have both types listed (although they're always on backorder)
V1 6-channelV2 6-channelV2 8-channel
RCModelReviews.com, just the facts.