When he is in Stockholm he might want to have a look at:
Repulsive Records, never been there myself but friends love that place, location: St Eriksgaten 84
Sound Pollution, never been to their physical store but I buy a lot from their webshop, location: Stora Nygatan 18
If he makes a pit stop in Västerås he might wish to check out Skivbörsen, excellent store and awesome personnel, sometimes a bit overpriced on vinyl, location: Stora Gatan 36, it is in an alley so it can be a bit tricky to find it.
There is a very small 2hand store (books, magazines, movies, records) near Espoo trainstation. With luck you might have to pay 15 euros for scratched copy of Denim&Leather. (Helsinki-Turku train stops at Espoo station.)
Also one vinyl section in a antique store in Tapiola (suburb in Espoo, 25 minute busride from Espoo trainstation).
99% chance that he won't miss anything special if he does not come to my lovely hometown.
Göteborg: Andra långgatans skivhandel + Disc Union. Both shops located on Andra Långgatan. And some other shop (can't recall the name) on Storgatan (short walk from Avenyn, easy to find).
Motala ---> go to Linköping instead, Crazy records on Vasagatan (opposite the theatre, some hundred meters of walk from the train station).
I too am traveling to espoo/helsinki soon, more record stores recommendations are definitely welcome...
I'm also interested in finding a good source in said area for experimental/noise/electronics etc. records, specifically looking for Swans items. If anyone knows any good places, please let me know. thanks.