You may be interested in these lapel badges that can make life just a bit less difficult for travelling on public transport when you have no visible disability or other signs that would help others to know that you would really welcome a seat:
community.macmillan.org.uk/...
You can go to their website and obtain a badge here:
Diaphragm hernia surgery 
Lanzoprazole and side effects
Post op sleeping position 
Swallowing difficulties 5 months post-op
Diabetes and oesophagectomy 
