Other option is to look at Gowin, like SiliconWizard suggested, or look at Anlogic. They have the AL3 series that resembles the Altera Cyclone IV series.
Yeah, that was nctnico actually.
Now while we don't know exactly what the OP's requirements are, they said the XC7S15 looked like a match, and from this: "My existing chip has 3000 4-LUTs and is around 90% full.", it would definitely be more than enough (unless the old design used some particular feature of the FPGA that would require a lot more LUTs on the XC7S15). The easiest would have been to just tell us what the FPGA they are currently using is, and what frequency the design runs at.
It's very possible they could even go for a lower-end FPGA than the XC7S15, such as in the iCE40 series or something. Since they mentioned a Lattice part (but which one was it), most of their deprecated parts are relatively low-end stuff from what I remember, so that should be no problem.
Not sure off the top of my head what is EOL at Lattice currently. I'd suspect either the MachXO (not 2 or 3), or old CPLD, or...? Or maybe XP2, is it EOL?