Sure!
The series is on a site called bookwalker here: ヨコハマ買い出し紀行(マンガ（漫画）)の電子書籍無料試し読みならBOOK☆WALKER
I like that site very much as I’ve found it easy to use and access even though I don’t live in Japan, and the selection is very broad.
The site often has sales and free books (both free to keep and free to read within a limited amount of time). You can find more information about free stuff in this thread: The BookWalker Freebies Thread
For a while after learning about bookwalker I often browsed a search query I bookmarked that tries to isolate all of the free-to-keep full manga volumes (and prose books but those don’t come up nearly as often).
And anyway, at some point the first three volumes of ヨコハマ買い出し紀行 were free-to-keep, so I picked them then.
Hope that helps! Learning about bookwalker (and other similar sites like Booklive) is definitely one of the best things I got from this forum! If I’d learned it sooner I probably wouldn’t have those physical editions… they are cool though…