You can select Products of the corresponding supplier.

"How to add supplier field in Sales order form? [closed]"

Check this Question.

You have to create domain, or filter on the product

Apply domain="[('seller_ids','!=',[])]" in field of product_id of sale order line.

<field colspan="3" context="{'partner_id':parent.partner_id, 'quantity':product_uom_qty, 'pricelist':parent.pricelist_id, 'shop':parent.shop_id, 'uom':product_uom, 'force_product_uom': True}" name="product_id" on_change="product_id_change(parent.pricelist_id,product_id,product_uom_qty,product_uom,product_uos_qty,product_uos,name,parent.partner_id, False, True, parent.date_order, product_packaging, parent.fiscal_position, False, context)" domain="[('seller_ids','!=',[])]"/>

Hope this helps.

Thanks, Serpent Consulting Service Pvt Ltd