Good sleeping bag as it might be frozen cold during tea houses stay as well as camp stay, for this you can either purchase the one in your home country or can hire one from any trekking stores in Thamel.’
Down good jacket, of course good one either rent or buys in Thamel.
Good sunglasses, polarized one in highly recommended as sun is bright enough, and sometimes need to walk over snow for a long time is worse condition with high chance of snow blindness so polarized sunglass is highly recommended.
Head lamp, as because of lack of electric power, mostly people in high elevation area does depend on solar power so in order to save the limited energy in high alpine area it is wise choice to carry personnel head lamp with changeable external power source and couple of batteries.
Buff, You will not regret for the decision of buying buff from Thamel as long exposure of skin from faces and neck in extreme cold and hard sun, skin burn is common as well as any kind allergies might occurred so it is better to have a pair if buff.
Sunhat, Not too fancy but good enough to block straight ray of sun over exposed body part.
Trekking poles, it is most as it helps a lot during downhill as well as uphill but for the people without practice of using trekking poles might feel it as bourdon but it is safe mostly downhill as well as makes easy for uphill so better to have practice of using trekking poles which you can do on plain flat before getting used too with this useful stuffs.
Hand sanitizer and small bar of soaps for body and clothes are most as it is kind of challenge to stay fit in high alpine area better to get rid of bacterial problems which might end on food poisons, so keep your hand clean all the time with help hand sanitizer but make sure about alcohol level more than 50 % on sanitizer.
Full first aid kit, although registered trekking guide do posses all the necessary first aid kid for emergencies situation but it is wise to have own personal first aid kit