Enabling TRIM on third party SSDs
You can enable TRIM on third party SSDs by using a tool called Trim Enabler which "works by patching a kernel extension, and also includes some SMART data to check the health of the SSD drive". 
I don't know if buying similar drive will get you TRIM to be auto-enabled in Lion. User @kukoo reports that he has bought an OEM-SSD which auto-enabled TRIM in Lion after installation. 
According to user @bmike, Apple usually uses custom firmware . 
Is enabling TRIM necessary?
User @cksum has covered this as a part of his answer to a post "Optimize MacBook Pro for internal SSD+HDD drives".