We had a Hauk Dream n Play when my grandchildren were babies. Currently selling for around £40. It was very handy for taking to hotels, self catering accommodation etc. The reviews were very good. I bought it in Tesco.
Be prepared for a travel cot mattress being much firmer than a regular cot mattress. The advice from the Lullaby Trust is not to be tempted to pad it with blankets or anything else to soften it. For safety, if an additional mattress is required it should be the custom fit one with correct measurements and no gaps.
I didn’t buy an additional mattress as my grandchildren slept as soundly in it as they did in their deep sprung cot mattresses at home.