Larry
The best way to find what you need is to go to EverythingRF and type in the freq band (in MHz) and you will see more options than you will ever need. Hopefully this link retains the search parameters (freq 4000-8000 MHz, gain 4-6 dB)

https://www.everythingrf.com/search/microwave-rf-amplifiers/filters?page=1&country=global&sfrequency_min=4000&sfrequency_max=8000&sgain_min=4&sgain_max=6

NOt all companies have their products on EverythingRF. fRor low gain amps you can look at Miller Microwave

http://www.millermmic.com/product/products_lna.jsp

Engin-IC has some tasty amps as well.

http://www.engin-ic.com/amplifiers/

I hope this helps
Steve

fRor low gain amps you can look at Miller Microwave.