Ferrex 150. It’s cheap. Feramax 150 is another but it’s so much more.
https://www.amazon.com/Major-Ferrex-150-Polysaccharide-iron-Complex-Capsules/dp/B01N5MH5R5/ref=m_pd_aw_sim_sccl_2/142-1733164-3713510?pd_rd_w=WSlQE&content-id=amzn1.sym.61a21ed3-e0dc-4600-88de-364bd56d9e86&pf_rd_p=61a21ed3-e0dc-4600-88de-3...