Speaking for myself - I have plenty of stationary (and books on writing). What I yearn for is uninterrupted time for myself and inspiration.
I try to go to The Brontë Museum once a year - you can buy the ticket and use it as many times as you can visit in the year. There are other writers houses - it depends on where your friend lives and who they might be interested in. I normally spend several hours there - the staff are brilliant and there are backroom staff who are happy to answer any difficult questions - I think it's an absolute gem of a place.
I remember a very special day writing at a fantastic location - this was at the East Ruston Old Vicarage Garden (Norfolk) - I took my notes and had a whole day to myself writing there - maybe you can think of a place, a nearby National Trust property with a nice garden and pay for the entrance fee, tea and cake.
There are no end of books about writing but one that I actually dip into a lot - and I've had it for years - won't be one of that ever gets mentioned - it's The Bloodaxe Book of Poetry Quotations (Contemporary Quotations on Poets and Poetry) by Dennis O' Driscoll -
{he wrote an awe inspiring book "Stepping Stones" (Interviews with Seamus Heaney) - IMHO - you don't have to be writing poetry to get something from these interviews with one of the greatest writers of our time - Heaney has a brilliant mind and he interviews so well - he's very lucid - I find him the most engaging and inspirational writer to listen to}. I'm a fan of interview collections, letter collections and diaries (e.g. the 2 volumes of Plath) - who is your friend interested in or inspired by?
The quotations book is just a place to search for some topical inspiration - there is a lot about writing and it's struggles but it's also often lightly amusing - it's a very curious and insightful collection of quotes (imho) and being a collection of pithy ideas, it's very easy to dip in and out of: probably not what you might think as right for a fiction/novel writer but - poets are writers too! Does your friend have any interest at all in reading or writing poetry?
Bookmarks! I have plenty now but that's because I've finally got round to ordering some ones I find that I liked - I like having 10 or 20 spare ones.