i have just purchased a large batch of 100uf 16V solid tantalum capacitors (surface mount)
these are vishay PN: 293D107X9016D2TE3
they can be used to replace any 100uf cap rated 16V or less (16V, 6V, 6.3V Ect)
heres a comparison picture showing the silver aluminum cap common in the duo and express and these caps (black rectangle)
I just got some 33uf 16V solid tantalum capacitors (surface mount) and am offering both now.
I'm offering these for $0.20 each plus shipping.
please look these parts up on line, you should be impressed!!
Tantalum caps are commonly used in aircraft and medical systems due to extreme reliability requirements in those systems.