I don't have any actual advice, per say, just wanted to share my experience - as it seems we are going through the same thing....
My LO is 5 months too and we introduced a bottle around 5 weeks and after a little bit of coercing, he took it once he realized it wasn't a paci and had some milk coming out of it. He took a bottle back in January when I had to EP for a week, and again in February when my MIL was here. Lately though, he's had a huge interest in cups and spoons despite that he is still EBF and he's become and extremely efficient nurser - he finishes up in about 3 minutes MAX per side.
I had to leave yesterday and I left DH with a bottle of thawed milk, and a warning that DS might not take it (I dunno, I just had a hunch.) and sure enough - he wouldn't. He wouldn't drink the milk from a sippy cup either (although he loves drinking water from one - only about 1-2 oz a day for fun)...I was about 45 minutes from home, so DH ended up spoon feeding him the milk, and I think the only reason that worked is because it was "fun" for DS.
I think the problem is that now he is set in his ways. He only ever drank from a bottle those few times, so even though he took it when he was younger - now a bottle isn't as efficient for him. I think the flow was too slow and same with the sippy cup. I did buy some fast-flow nipples yesterday and tried one last night just to see, and he rejected that too. I think it was too fast. I am going to work on getting him to drink more efficiently from a cup - and that way if I have to leave, he can drink the milk from a cup instead of a bottle.