uxcell DC Male Connector 5.5mm x 2.1mm x 14mm Power Cable Jack Adapter Coupler Black 10Pcs

Agree with the exacto knife solution. I use power supplies with shorter tips, but the housing is small enough for a nice fit. Also, here is another option if you go with soldered solution (I use these in my restorations sometimes):https://www.amazon.com/dp/B07MJG5RFP?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2 That said, I like the first link from u/FreeRangeEngineer - Probs the best solution if you don't want to solder or use a blade. Also, just to say, most 2.5mm adapters (at least all that I've run into) have an internal spring to grab a 2.1mm shaft.. but it's possible some do not.