I have old mailing labels and print my Non-Machinable tags, bulk.

As of January 2024 new rates:
1oz = $1.12
2oz = $1.36
3oz = $1.60
3.5oz = $1.84

3.6 - 5oz it's a Large Envelope (I mailed one item, $5.15 in January, but no promises)
at 6oz a large envelope if rigid becomes a small package.

But for non-machinable, get the forever butterfly stamps, add 24¢ for each additional ounce. Limit is 3.5oz for non-machinable.

Have fun? Remember if the address is not in the right orientation or is too close to the edge, you may be non-machinable. Too thin? Uneven thickness, and 1/4" is the maximum allowed thickness of a mail piece. Can't be square.

3-6 Nonmachinable Criteria

A letter-size piece is nonmachinable if it has one or more of the following characteristics (see DMM 601.1.1.2 to determine the length and height of a mailpiece):

Has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5.
Is polybagged, polywrapped, or enclosed in any plastic material, or has an exterior surface made of a material that is not paper. Windows in envelopes made of paper do not make mailpieces nonmachinable. Attachments allowable under applicable eligibility standards do not make mailpieces nonmachinable.
Has clasps, strings, buttons, or similar closure devices.
Contains items such as pens, pencils, keys, or coins that cause the thickness of the mailpiece to be uneven, or contains loose keys or coins or similar objects not affixed to the contents within the mailpiece. Loose items may cause a letter to be nonmailable when mailed in paper envelopes.
Is too rigid (does not bend easily when subjected to a transport belt tension of 20 pounds around an 11"-diameter turn).
For pieces more than 4-1/4" high or 6" long, has a thickness less than 0.009".
Has a delivery address parallel to the shorter dimension of the mailpiece.
Is a self-mailer that is not prepared according to the DMM.

Bravo for making things so impossible that the mail clerks don't usually understand these regulations.

https://pe.usps.com/cpim/ftp/manuals/dmm300/601.pdf