I use KINEK at Wellesley island building supply just 2 miles across the Ivy Lea bridge. I used to use UPS in Watertown. You can also get a flat rate box at the post office next to KINEK.
If you're shipping via UPS, you should be able to use the UPS Staffed Customer Center in Watertown as your shipping address for free. I use the one in Buffalo, NY regularly.
