Youbcan get a letter signed by your colleague or supervisor on plain paper with all the necessary info as per CIC requirement. Get this letter notarized and write a LOE and attach supporting documentation to prove this job
The main reason they ask for the letter is to verify that duties match with those of the noc. If the notarized letter from colleague/supervisor has the duties listed, pay stubs, offer letter, bank statements should suffice as supporting documents.