Most small growers use a good ol' white grease pencil on the flat and often on each individual pot. Since the pots and flats are dark the white shows up well and stays for quite a long time. The other answer is google "horticultural labels" and there are a bunch of companies that sell bulk labels for a jillion varieties.
It is possible to get your business name on the individual labels, but that adds bucks to the cost. You might consider a single stick label in OR permanent sticker with your name and logo on all pots, then grease pencil an acronym on each container (BBT = Better Boy tomato, JST =Jet Star, etc.) for sure ID.
Good luck with the biz.

how about a ptouch label maker? there are heavy duty adhesive labels available. The software runs a PC and you can add small graphics. You would need to peel and stick the label on a regular stick and decide if its per-pot or per-flat.

If these plants are going to a retail nursery, be prepared to have tags with all relevant info--name of plant, conditions under which it should be grown, description of vegetable, etc. These are readily available for common items from several tag companies, but there could be several weeks between order and delivery.

For your business ID you could have separate tags custom printed with just that info.

It's late in the game to go the route of custom tags which list you as the grower somewhere on the plant tag. You'd be doing good to get your business info on an order of plain tags in time for this year's plantings.

Customers expect tags with info, and preferably in color with a picture of the vegetable. Grease pencils would never cut it in the area I live.