Thanks for the suggestions so far.
Get a chameleon suit w/ Thermal dampening and a ruthenium polymer poncho.
Teamwork checks help to raise your limit and give you bonus dice (sneaking might take longer that way)
Valid one; I'd actually been eyeballing this already and thinking it was probably necessary as long as I could find additional methods.
Use drugs for improved agility and detox afterwards. There is even a BTL chip for would be cat burglars - get a hot sim enabled commlink and a trode net to slot one of those (preferably one that doesn't burn out) as a mage you should be able to withstand the compulsions and the addiction.
I had considered this; while viable as a suggestion, neither are really "in character" for my mage to engage in.
Initiate and learn the masking technique + a decent metamagic focus.
Maybe I've misread masking. I know it can help conceal foci, but are you saying this can also conceal that you have a spell active? Or are you saying that, given casting invisibility isn't going to be an option, this is an important step combined with many others to get concealed?
Besides all that Jack Spade mentioned, there is another option -- although it is painful for a mage to put karma anywhere other than magic -- buy up your agility and stealth. If they are low now, the cost won't be too brutal.
This is true; but, to match the lowest sneak of the group (the others are much higher) would cost me 67 karma. This is a ways off - my mage has spent almost his whole life up until three sessions ago as an academic at MIT&T, leading a cushy life, until a serious of unfortunate events essentially destroyed his ability to get respectable work of any kind. His agility and sneak are as low as they can be.

In the shorter term, spirit concealment power can help a lot, when you can get away with using it.
Doesn't this suffer from the same limitations WRT astral watchers as with casting invis on myself? As I understand it, concealment is basically just a physical power that will show as very obviously active in astral space.
Also, GM might want to consider whether always breaking your concealment spells is a fair way to treat you as a player.
I dunno. Our GM knows SR pretty well, and the interpretation is that if you have active spells, then you pretty much glow like a lightbulb to anyone with astral vision. I'm just surprised that spirits, dual-natured guardians, etc, are so common as to make concealment spells dubiously useful to a runner.