You can interview in a country that is not eligible, sure (we have many people interview in the UK every year for example), but in order to change location you need to have a permanent address and some form of legal residence there (work, student, etc). Depending when your case number is current you may delay the interview by changing location. I would also advise you to investigate the status of immigrant visa interviews at Dhaka given that many embassies are still operating at reduced capacity and giving priority to interviews for family of USCs. You may find it is better for you (not saying it is but it may be) to fly to Colombo for the interview rather than trying to move it.
You do understand you will have maximum 6 months to use your diversity visa, correct? Just asking as urgent relocation ahead of being issued an immigrant visa for somewhere else seems a little contradictory.