Baby monitor!!!

Hi, my little boy has trouble breathing especially in his sleep. We'll be discharged soon out of hospital, but there is one problem. At home we don't have anything that would watch over our baby's heart rate and oxygen. He is only 8 weeks old, I'm terrified. Is there any monitors that are good and not too expensive?. Unfortunantely i don't have 200£ for owlet smart sock baby monitor.. 😭just too scared to be at home, I won't be able to sleep. He had quite many episodes of oxygen dropping in his sleep esspecially in the night time.. he was on oxygen for 2 days straight as his levels were dipping quite quickly and he got grey/blue colour to his skin. He would not wake up when the oxygen dropped and if we were at home it probably would have eneded not so good.. 😢😭😭😭 please any advise?