Theoben sell riser block for £17 which fit on the lower scope mount to give another 10mm of clearance.
Dampa mounts are only available in 1" size.
30mm two piece mounts are available for all the Gas rams (£45) but whether they are suitable for the Eliminator, you would have to check the scope mfr spec and maybe email theoben.
I am surprized that you cannot mount a 50mm scope on the standard mounts, maybe it is a PA one, adjustable objective, so larger bell end?
The products above are on their web site.
www.theoben.co.uk