I've received single chips or even multiple chips (maybe up to 2 or 3) this way in the mail with standard envelopes via purchases from a few well rated
eBay sellers with no problems. However, those sellers have also paid a Non-machinable Surcharge which is added to first class postage, which is so the USPS doesn't run the envelope through their letter sorting machines, which could damage the chips or tear the envelope. IIRC, the seller wrote "NON MACHINABLE" in red print on the front of the letter at the top or left. (If taking letters to the post office desk, maybe the post office clerk stamps this on the envelope themselves. I'm not sure.)
Through Google search I found:
Regular first class stamp 49 cents. (first ounce, additional weight is more)
Each additional ounce 21 cents
Non-machinable surcharge 21 cents