It's unfortunate because the Deluxe Mistress is a fairly unique flanger that sort of blurs the lines between a chorus and a flanger. Most other flangers are really more about the airplane whoosh than about the subtle filter movement.
So your options are fairly limited, honestly the Mooer is the only super cheap way to get that kind of tone that I've found. Most of the current Deluxe Mistress flangers don't sound quite right to me or have issues with tone suck.
A fairly decent solution could be the TC Electronic Vortex Mini:
http://www.tcelectronic.com/vortex-mini-flanger/ When you buy the pedal it might not sound like a deluxe mistress but you can download different tones to upload into it, and a bunch of them are geared towards doing the Andy Summers/Deluxe Mistress thing really well.
Heres a video of someone using the Vortex (large version) to that end:
The other option of course is to go with a chorus pedal, as Andy did later in his career, a Boss CE-2 or clone of that (of which there are many).