I think that because it is only a few occasions, the pumping/expressing is the more important thing for your comfort and supply and I wouldn't worry too much about whether LO takes to the bottle or not (unless you are planning bottle feeding further down the line) as a baby that age isn't going to starve because he went 6hrs or so between feeds. Yes it will be upsetting for whoever is looking after him if he's upset, but I think that'll be more to do with you not being there than being hungry. They can always try cup or syringe feeding him if necessary.
I realise it sounds like I'm being harsh and saying "babies need to get used to not feeding so often" but I am NOT at all. What I mean is that given the fact that it isn't a regular occurrence and LO may well be off his feeds just due to your absence, it would be a shame for you to spend weeks (and lots of money) buying lots of different teats, swapping breastfeeds for bottle feeds, expressing for these "trial feeds" and for the time you will be away too! It sounds exhausting. I mean if you are happy to do it as it would reassure you he could be fed then great, go for it. I'm just saying you don't necessarily have to.
Is there no way that whoever is looking after him could bring him to where you are working during a break so you can feed him there?