You can't really emulate TRIM, as the TRIM command passes information on which blocks are freed up and that information is long gone.
If the drive implements Garbage Collection (have to look up the specs to see), leave it powered on but idle overnight and it should do cleanup. Otherwise. thou art hosed.
There is an extreme solution. Do an image backup to an external hard drive, booting off a USB key or a floppy. Test it, since you are going to be betting the farm on it. Download the Secure Erase utility and have the SSD Secure Erase itself. Now it knows that all the blocks are free. Restore the image. Only the used blocks will be marked as used, and you will have 100% GC for one brief moment.