Shane Cusick, founder of Pello, a children’s bicycle maker, has seen sales of his orange-colored bikes grow to around 400 to 500 a year. Because he has been unable to find domestic suppliers, Mr. Cusick has sourced his lightweight bikes from China. He has been reluctant to pass along the 10 percent increase that came with tariffs imposed on imports from the Asian nation. Now, he’s trying to figure out what he will do with a 25 percent tariff on the way.