The cheapest way is to do it yourself. Buy the chip and it's in an applicator ready to be inserted. If you're worried about the size of the needle vs the size of the snake just wait until it gets bigger. You can still send the Cites back and get it amended with the chip number put on.
Some years ago I sent off a batch of Tortoise Cites with the microchip numbers to get them amended. When I got them back it stated...'One live Tortoise wearing microchip number........' I had visions of the Tortoise with a chain round its neck with the microchip hanging off it!!
It's relatively easy to implant a chip in a Snake but I've never done it with a Tortoise. You can see the size of the applicator and especially the needle below. I don't know about anyone else but I wouldn't want that needle stuck in me. Think about the size of a Tortoises' leg when it's Plastron is only 4" in length (the size you should get a Tortoise chipped). That's why I've never attempted to chip a Tortoise!!
