You've gotten some great advice. I'm not sure if anyone has mentioned this but if the people who do your draws are familiar with you, you could ask that they use a doppler to locate your vein and do the draw/administration. That could help a lot.

As far as visibility goes, the port-a-cath is pretty much invisible (not to mention has a much lower risk of infection) because it's surgically implanted, I doubt a doctor is going to give you one just for having bad veins. Perhaps if you were on Ty and couldn't get your infusions due to the condition of your veins but even then it's a long shot.

Take care.