Hi I am planned to purchase things to give as BhikkhuSangha Dana. I planned to invite four monks at a local Theravada Monastery and do the offering.
Among the items, I planned to buy slippers and umbrellas for the monks. But may I know what kind of slippers and umbrellas are not allowed in Vinaya?
Please can guide?
According to the great standards, rubber slippers are allowed as “leather”
You could also go with leather.
Cork soled slippers are controversial because they are made from wood.
You cannot have cloth straps. Be careful about woven cloth used for the anchor for the straps.
You cannot have slippers made from rope.
Umbrellas… I’d have to look that up. Some different opinions exist what can be used inside the monastery and what can be used outside… and the color.
It would be best to directly ask the monks of the community where you wish to donate what they think is allowable.
Thank you Bhante for the information. 
Just to update, I went to a Sri Lanka Theravada Monastery (there I believe is good as they adopted orthodox Theravada tradition), and I made the Sanghadana along with my family.
I told the monks and the office members that I hope can request two Venerable monks as a representative of the Sangha and I shall perform Sangha Dana, as accord to what was taught in Dakkhinavibhangasutta.
"Ettakā me bhikkhū saṅghato uddissathā’ti dānaṁ deti—ayaṁ chaṭṭhī saṅghagatā dakkhiṇā.
One gives a gift, thinking: ‘Appoint this many monks for me from the Saṅgha.’ This is the sixth religious donation bestowed on a Saṅgha."
I offered the Sangha Dana, together my family members also joined. I felt very happy.
Next month, I will perform a bigger Sangha Dana (during my birthday) and with the office’s and monks’ permission, I have requested for four Venerable Bhikkhus to present as representative of the Sangha.
I am happy about it. Planned to do it every month. And my sister said she will perform every month too.
sadhu x 3.
Happy before
Happy during
Happy ever after.