This is a genuine GM pressure cap. It’s the latest design and part number that fits the SSR. Retail price for this part is $17.98.
This is the part recommended for all SSRs, 2003-2006.
It’s important to have a good seal on the side-mounted o-ring in order to hold proper pressure on the cooling system.
I strongly recommend replacement of this cap every 4-5 years, as the o-ring tends to go “flat” and could be responsible for “higher than normal” engine temperatures due to lack of proper system pressurization.