vitamin B1,
Is there a specific reason you are only looking for B1 rather than a full B complex? Your other B levels can be problematic, too, so most surgeons recommend a B-50 complex or B-100 complex daily.
Rather than take 5,000 units of D3 daily, many of us opt to take the 50,000 unit D3. It is available online from a number of places including www.vitalady.com or Vitamin Shoppe. It is also available at Vitamin Shoppe stores.
My surgeon did not require, or even suggest, a probiotic. Many people rely on yogurt for their protein needs, though, (especially early out) and yogurt is high in probiotics, so a supplement would probably be overkill. I would ask your surgeon, though.
Lora
14 years out; 190 pounds lost, 165 pound loss maintained
You don't drown by falling in the water. You drown by staying there.
I think most places that sell vitamins will sell thiamine. You may have trouble finding 5,000 IU D3 in stores, especially in a dry form, which we need (that just means a dry tablet or a capsule with dry powdery stuff inside, not those softgels with oily stuff inside). A lot of people here order their D3 from vitalady.com. She has large doses, too, so you could get the 50,000 IU D3 and take it once a week instead of taking 5,000 IU a day. Just FYI, most post ops need at least 10,000 IU D3 a day to maintain a good vitamin D level.
Kelly
Please note: I AM NOT A DOCTOR. If you want medical advice, talk to your doctor. Whatever I post, there is probably some surgeon or other health care provider somewhere that disagrees with me. If you want to know what your surgeon thinks, then ask him or her. Check out my blog.
The reason we absorb a dry form better is because we malabsorb fats. Oil is fat, so we don't absorb vitamins in oil as well as we do dry forms.
Kelly
Please note: I AM NOT A DOCTOR. If you want medical advice, talk to your doctor. Whatever I post, there is probably some surgeon or other health care provider somewhere that disagrees with me. If you want to know what your surgeon thinks, then ask him or her. Check out my blog.
I want to suggest that you follow your levels closely by getting blood work done regularly and taylor your supplements depending on what your levels are. Not everyone needs really large doses of vitamin D to maintain a good level. I wasn't supplementing with D for a long time as my surgeon didn't list that as one I would need, but then I kept seeing on here where everyone took D and in large doses. So, without getting my blood work checked first, I bought sublingual D3 in 5000 IU and started taking it daily. When I went for my regular lab work visit, my D was high. My doctor told me to cut back on it. In order to keep my D levels at the high end of the normal range, I take 1000 IU sublingual D3 four days per week. I get my blood work done regularly so that I am not over or under taking any supplements because some supplements can be toxic if your levels are too high.
I do take a probiotic daily because yogurt makes me sick, and my intestines got out of whack at one point so I was told to take a probiotic daily. Not everyone needs one, though. This life after WLS is somewhat trial and error as we are all different and our bodies need different things. Good luck to you. You will figure it all out as you go along. 
