Hey, Tinman, I have one as well. This is my first 22 semi auto rifle I got as soon as I could legally purchase one in 1978.
Great little rifle, i have a 10/22 as well. But I found the trigger better on the 490, and as is, it certainly was more just a little bit more accurate than the standard ruger.
I used it for many years gopher hunting in Saskatchewan, and I found that after 300- 400 rounds I had to detail strip the 490 to get all the carbon out that would build up and jam the rifle.
Really the fact that i could buy larger capacity magazines for the ruger, and the ruger would last to almost 800 rounds before requiring cleaning, was the only reasons I picked up a 10/22.
And no there are no presently made mags bigger than 10 rounds available that I am aware of.....for the 490.
I believe they stopped making the 490 in and around 1976-77.
Western Gun Parts, was my source for spare parts, just cause they do not catalogue some firearms, does not mean they do not have one or two parts rifles in the warehouse.
You have a nice Canadian made, 22 semi there Tinman.
There are many poorer quality 22 rifles out there, going for more money than they are really worth!
Cheers........