Brief Answer:
You would need to get the TMP-SMX antibiotic from a compounding pharmacy.

Detailed Answer:
After doing some research into this, I found that there are no existing forms of Trimethoprim-Sulfamethoxazole that do not have artificial coloring or flavoring.

One pharmacist I spoke with suggested that it may be possible to have it made by a compounding pharmacy by crushing a tablet/powder of the antibiotic and mixing it with a suspending agent. This would require a prescription from the doctor for the compounding pharmacy to do so.

I see that you have a compounding pharmacy in your area:
Address: 2310 Mildred St W #138, XXXXXXX WA 98466
Phone:(253) 564-2323
Hours: Open today · 9:00 am – 6:00 pm

You may want to give them a call to see if they are willing to compound this for you, and what order/prescription you would need to provide them with from your grandson's doctor.

I hope this works out for you.

Please let me know if there is any further information of clarification I can provide.

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Brief Answer:
A list of compounding pharmacies in the state of XXXXXXX

Detailed Answer:
I found a general list of compounding pharmacies in the state of XXXXXXX
http://www.ecompoundingpharmacy.com/local-compounding-pharmacy/Washington

I see that one is listed for Kirkland, but I don't know if it is currently in operation nor if it will compound an antibiotic.

http://www.ecompoundingpharmacy.com/compounding-pharmacy/Juanita-Bay-Pharmacy,26642#.VaQGxc56o5Q

If this company does not compound antibiotics (as they do not list that they do on their page), try one of the others in larger cities, such as the XXXXXXX company, and see if it is possible to have the medicine mailed to your daughter.

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