Either cubed, or just the dehydrated powder.
I've searched hi and low and found that chicken, beef, vegetable and fish are pretty common. Finally found my Aurora herb & garlic cubes @ Branche D'Olivier. Got the S. Martino basil cubes after a long hunt. Mushroom can be found here and there. Both P&A and Branche d'Olivier, among others, carry the many varieties of the "Harvest Sun" line (including onion). Asian supermarkets have endless fishy and non-fishy cubes, many of them of the "Maggi" brand, the exact flavor being unidentified, or simply said to be "MSG/flavoring".
So it's a little complicated, but I can't use tomato paste. I have resorted to running pouches of Campbell's tomato & vegetable soup mix through a colander to filter out the noodles and veggie bits. The remains are perfect, though - exactly what I am looking for: dehydrated tomato powder.
Any ideas as to where could I find such a product in Montreal?