Newbie airgun question

I just bought a Gamo TAC Whisper air rifle so I can learn to shoot left handed. I am left eye dominant but have always shot every weapon right handed. But I've been diagnosed recently with wet macula edema in my right eye so all reticles are a tad blurry. So I want to learn to shoot with a scope left handed (I tossed the included scope in favor of a better scope that I had).

I like the rifle and I got it sighted in fairly close with just 2 shots at 45'. My only issue so far is there is no place to add a sling swivel at the top end, as the barrel move downward through the top of the stock in order to cock it. Just wondering what others have done to solve this and add a sling to their air rifle? Thanks.
 
You can do this-Make sure you get the right size for your barrel.
images

http://www.midwayusa.com/product/1398650630/uncle-mikes-quick-detachable-magnum-band-sling-swivel-set-1-black