I really hope soon, been allready too damn long.
Will try to educate the customers in the future but untill then im stuck ....
You can try to re-spend the output. Send it to another address that you control and include a fee large enough to compensate miners for both transactions.
If any miners have implemented the "child pays for parent" concept, they may confirm both transactions at once to get the fee from the second transaction.
Honestly, I don't think any mining pools have implemented the concept yet. I really think they should. It would provide increased income for the pool and would solve problems like this.
Unfortunately, I don't think this is a great idea. It creates a moral hazard where senders don't include fees with the expectation that the recipient will make another transaction with a lot of fees if they really want the coins that badly.