Compass - useful for GNAV and DME arcs etc.
Non Programmable calculator - Something like the FX-83MS. Have seen them quite cheap in ASDA from memory or it could have been Tescos. It has hours/mins/secs which is again really useful when you get to GNAV and are doing flight time problems.
For the CPL/IR the best thing I ever brought was and airways plotter. Great for when you had to plot your position based on a VOR.
http://www.flightstore.co.uk/prod/FVP1/DEPT-ACTS/PLOTS/