Size 3 is perfect for 150mg, try these they’re my favorite to use, blue and green!
https://www.medical-and-lab-supplies.com/green-blue-size-3-rls-c372-gelatin-capsules-bag-of-500.html
And this funnel fits perfectly in it
10 Pack Small Metal Funnels with 2 Pack Mini Pipette for Filling Small Mini Bottles or Containers, Atomizers, Perfume, Liquid (Silver) https://www.amazon.com/dp/B07DDJ48DC/ref=cm_sw_r_cp_api_glt_i_1Q4TMK3JRMXQ31K88JYF?_encoding=UTF8&psc=1
You could buy the funnel, keep 1, and return the rest for a refund, Amazon doesn’t count