It’s been about 5 years since I bought my eBags Mother Lode TLS Weekender Convertible and it has been with me on around 8 overseas birding adventures now and is still going strong!  This bag is really sturdy, hardly weighs anything so you can maximize a 7 kg carry-on limit.  It easily holds a DSLR, 100-400mm lens and several changes of clothing although you should always wear your heaviest shoes on the plane.