You'd be able to pick up the generic holders at pretty much any supplier of cutlery (a huge number of high street stores). The advice re the original supplier sounds good as having one to match the size of your press would be beneficial.
Mrs Cu get her long awaited new kitchen and it was fitted with 'blum - orga-line' cutlery drawers. They can be changed around (a bit anyway) and she's happy with them
I've been looking for one for ages for my top desk drawer, as pens and staples and all fly around loose. Can't get one of those pen holder things that only takes up half a drawer as I think they only sell them with the desk - and mine never came despite repeated requsts to the company. Off to Woodies so!
Gordanus - if you are in Dublin, you could try Muji on Chatham St for pen holders etc. Not sure if they have the desk-drawer tidies, but lots of plastic trays/jars to keep 'odds & ends' in.