Add Igniter'n'things vendor to Security. Or just straight up more Securitrons.

[Newtonsolo]

there's a vendomat in the same room as your lockers which produces those things which is presumably where you get the rest of the securitron components

According to the maps, that's only on Cog1. (and yes, I did not even notice that one, so thank you).

I think securitrons also need a robot arm to work.

You are correct. And if at all possible, a supply of them in the office would also be much appreciated.
Or just straight up securitrons.

i feel like you should still have to work to get robot arms and not just have 6 or so securitrons ready to build on a silver platter, additionally if you want more robotic security you could ask the rd to activate some of the sleeping buddies 
also the people talking about the "desks" and the "offices" it doesn't actually make you seem more official because we can't see you in there so it just gives the impression there isn't any security on the station