As far as the 'left' thumb goes I had an extended slide release installed on my 45 years ago. So my right thumb grabs the high extended safety down for a nice stiff grab and the left thumb had the same type of extension for my left thumb to hold the front end down. Worked like a hot damn. I think each part was around $50 but sure gives control of the gun well with rapid firing. I should order one of those from Brownells. They ship to Canada where most U.S. firearms dealers can't legally export their guns or gun parts. They can but with the very expensive licences needed most don't bother and have to sell within U.S. borders. Only thing with the extended slide release I had to cut a slice in my holster as that far into the gun the fit is fairly tight and no room for the extension. Don't really want to slice up my new holster so I'll try it without the extended slide release and just the extended thumb safety the gunsmith is putting on my 9 mil.
And up here guns are also flying off the shelf with parts hard to find especially with all the U.S. export restrictions. Wish I had bought Ruger stock that has soared with no risk to sales and profits it seems. The stock has tripled over the last year. I heard they stopped taking gun orders as they can't make them fast enough and need to catch up to their present orders 1st.