What satellite and band? There are sats that use UHF downlinks, and sats that use VHF downlinks. Which preamp to get depends on which sat and mode.
You might want to look up Advanced Receiver Research on the web. ARR makes some nice, fairly inexpensive preamps with low noise figures. I use one here for the UHF downlink. The preamps are designed to be powered by 12 VDC, so you could use a gell cell. They are available with or without T/R switching. Since you are using 2 radios, you probably would not need the T/R switching feature.
If I remember right, I think the receive only models started at around $80.
73, de Tom, KA1MDA
www.ka1mda.org