I've got a SilencerCo Omega rifle can, and I love it. It's not the cheapest by a long stretch, but it's light weight, full auto rated and rated for very high caliber use (All the way up to 300 WM).
One big caveat though - most cans that are rifle rated are sealed, I.E. you can't take 'em apart to clean 'em. And you do NOT want to shoot .22 (Or any lead only bullet) through a sealed can, the lead blowoff will build up and fill the can up, ruining it.
.22 cans are generally specifically for .22 so that they're much smaller, lighter and most importantly, built to be taken apart to have the lead cleaned out. (I've got a pair of SilencerCo Sparrows for .22 usage, love 'em)
The only "Swiss Army Knife" can I know of that's for rifle, pistol and .22 is the Liberty Suppressors Mystic-X, but it's only rated up to 7.62x39, can't use it on 7.62x51/.308.
Be careful though, once you've shot with a suppressor, it's hard to shoot without one. It feels so... uncivilized... to shoot without a can now. Not only is the noise level drastically reduced (No, they're not silent, but I can shoot .308 comfortably and safely with no hearing protection) but also the felt recoil is cut WAY back, and the muzzle flash is virtually eliminated.
I was sighting in my new Tavor (5.56) at an indoor rifle range a few weeks back, and first shot it a few times without a can for a basic functionality check, then put the can on and shot the rest of my session, and the difference really blew me away.
Yeah, there's a lot of paperwork, money, and waiting (I'm still waiting to get my 2nd batch of cans out of NFA jail that I bought back in August) but if you can handle those things, it's an investment well worth it.
But yeah, short version - a single can appropriate for .308 AND .22 is gonna be difficult to find, I would highly recommend he split that up into 2 different cans.
One other point to be aware of - A quality modern suppressor will not cause inaccuracy, however they WILL shift your point of impact. So you need to be sure to zero the rifle in the configuration you will use it in. At 50 yards my Tavor's POI was 2 inches up and to the right with the can on from where it was shooting unsuppressed.
Sorry, I got a bit long winded I see, but it's a topic I've recently gotten kind of in to. Feel free to ask me anything, I'm no expert by a long stretch but been looking into this area a lot lately. Getting me to talk about it is easy, getting me to shut up about it is the trick.

The upper right target is the with a can/without a can comparison.

