I agree with cerelac you can add it to yoghurt, cereal, smoothies.

Cerelac rice cereal with added iron. I usually mix in some pureed fruit and my babies loved it

I think I’ve seen breakfast cereals that have been fortified with iron, not sure

Spinach in a smoothie

Have you tried Cerelac or Farex. Both ricj in Iron and you can always add fruit pieces to it?

What about eggs? Or you could make a smoothie with banana, strawberries, yoghurt and milk and baby spinach blended down.

Is your little one getting iron from his other meals? If he’s getting enough throughout the day, breakfast may not be such an issue

Have you checked the ingredients on other packets of cereal? I’ve noticed that weetbix tends to go too mushy if it isn’t eaten quickly enough. Some little ones find them very bland (not much flavour)
They tend to soak the milk up quite quickly too. If he is getting enough iron in his other meals he may be getting enough. Does your son like toast with a smear of vegemite on it? There is similar in different brands if he is allergic to any foods at all (some are gluten free if that is an issue)

Have you tried an Omlette with spinach? Or any fortified cereals?

Eggs
Oats / oatmeal
Beans and lentils.
Tofu.
Baked potatoes.
Cashews / nuts or peanut butter
Dark green leafy vegetables such as spinach.
Fortified breakfast cereals.
Whole-grain and enriched breads.

Have you tried mushrooms? My little one loves mushrooms on their own