Help needed the controler wheel on my photon as come loose is there anyway to tighten it

I have photon side adjustment button as come loose is there anyway to adjust it please 
 

I've been interested in some time about investing in a night vision scope and been looking around and I have found that for my price range I have two options: the Yukon photon RT or the ATN X sight 2. They are both similar in price, however the ATN is slightly more expensive out of the two. I've seen them both on airrifleshop.com. I'll leave the links and id love to hear people opinions on what's better, as I'm not fussed paying more for the x sight, its just I've heard the photon RT is mint for the money.
https://www.airrifleshop.co.uk/collections/nv-scopes-add-ons/products/yukon-photon-rt-6-50s
https://www.airrifleshop.co.uk/collections/nv-scopes-add-ons/products/atn-x-sight-2-hd-3-14x
 
 

Hi just bought a new yukon photon 5x42 dose any one no where I can get a cheap doubler for thanks