RF substrate for S band design

Hi, :D

I am looking for RF substrate to design HPA board for space application in S band.

I encouter some difficulties to find high dielectric permittivity substrate on manufacturers website (like Rogers, ...etc).
I would want to find permittivity level higher than 50 in order to reduce circuit size but it's really hard.
If somebody has already worked with this kind of components....

Could you give me in this way, by giving me manufacturers names ?

Thank you very much.

Please help me

Try to find something that suits you on www.matweb.com.