I'm wondering if I could self-certify my application or should I find another CFI to certify my application?
The word used in 61.195(i) is “self-endorsement”, not “self-certification”.
Interestingly, there is no such language in Subpart I, Ground Instructors. Back in the 1980s, I had a Ground Instructor certificate and I endorsed myself for the Instrument Instructor written. The test proctor accepted it.
Last November, while I was still an FAA inspector, I entered an application in IACRA for a CFI renewal. Just for the heck of it, I went into IACRA to see if I could issue my own certificate. IACRA will not allow a person to process an application for his own FTN number. So, no. You may not process your own application.