http://www.marcospecialties.com/pinball-parts/4808-01175-08, You'll need about 100 of these.
http://www.marcospecialties.com/pinball-parts/4108-01115-06, for slightly shorter applications
http://www.marcospecialties.com/pinball-parts/4004-01003-06, for the top side
http://www.marcospecialties.com/pinball-parts/4006-01005-32, I like to have a lot of these on hand and cut to length in a pinch.
http://www.marcospecialties.com/pinball-parts/4006-01003-08

I'm sure there are quite a few more, but you'll never regret having these on hand.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact/
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

The parts catalogs have breakdowns of all mechanical components and give part numbers for all the hardware. It may be a bit time-consuming but you'll find the occasional onesies and twosies in game-specific components which aren't used elsewhere that you'll be glad you ordered. Here's the catalog that includes Pinbot:

http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_Blue_16-9064-B/index.html#/1/

At the Bunny Ranch they line the screws up and you get to choose.

Unless you've got a lot of missing hardware, you may have better luck cleaning your hardware up.

I'm not sure how much luck you'll have finding imperial sizes in Denmark.

What I did with my first restoration was to buy a junker of a similar era. Stripped it down, cleaned up the parts, and as I rebuilt things and needed a screw, a post, a coil, etc, I had some spares to work from.

Just an idea - if you want new, that's fine. Just thought I'd share what worked for me.

I can vouch for that.

Maybe buy a tubler to clean the screws up?
I can also recommend getting the little box of calm from Titan and the assorted screws pack from Marcos.

What?!?!
No part number for 2-1/2" deck screws?

No, you're not reading it wrong; in most cases Williams (and Bally, for that matter) did not provide that level of detail in either the game-specific manual or the parts catalogs. At some point part-way through the WPC era they did start including a hardware section in the parts catalog that lists all the hardware items (screws, bolts, etc.) used with a unit count breakdown per game title, but even then you had to rely on matching up the part you wanted to replace with an illustration in the game manual or parts catalog.