Easiest way to do this that I know off is by going on blockchain.info, because you don't need to download anything, you don't need any software to create the address and get the QR code. Of course, I would move my funds from there as fast as possible, can't trust anything but core tbh.
He is not asking how to create an address's QR Code.
You can do this in Electrum wallet in the Receive tab.
Sure other wallets should have this same functionality.
-snip-
But Electrum will only let you create requests from the address which are in the Electrum, you can't paste an address from outside and create a request payment code??
OP, try myb.tc
http://myb.tc/QJT/9.99USD <- This is the result, if I create a request for $10
Or use this:
http://www.btcfrog.com/qr/ This works, if I point my copay qr code scanner to it, the fields get auto filled with my address plus 0.02 in the amount field. I created it using btcfrog and uploaded the qrcode to imgur.