Dad refuses to bury my deceased mom after 6 years

Unsure of whether to drop this or push. My (41F) mom died young, at 60 after a 10 year battle with an aggressive form of dementia. Because she passed the first week of the COVID lockdown in March 2020, everything was a little backward. We only had a funeral 6 months later with a lot of restrictions. It wasn’t at all what I would have wanted for her but she did get a proper funeral.

I am the eldest of 3. I coordinated almost everything during my mom’s illness, and for her funeral. We decided to cremate my mom and I chose the urn. We decided she’d stay at my house because I bought the house I grew up in from my dad and am raising my kids there. She’s on the mantle and it’s lovely.

However - my mom didn’t have a will. I strongly believe she would have eventually wanted to be buried. She grew up in the countryside and there are plots she purchased and ready where her parents are buried. A place she loved to go to and that she held very dear. Problem is my dad refuses to let me coordinate or go forward on this last bit. He doesn’t want her buried. He refuses to give me the paperwork to go forward and just get even a tombstone made.

His argument is that he likes her where she is and doesn’t know where he’d like to be buried. He’d like me to wait until he dies and bury them somewhere together.

My feeling is that this is really only placing his needs and desires first, not hers. It feels almost like I’m betraying her wishes by going forward with only his plan. What would you do in this situation? My siblings are disengaged and side with my dad. Am I in the wrong to keep pushing?

EDIT: there is no urgency as some have said, the only real timely element is that one of my siblings and my mom’s sibling are visiting for the first time in 7 years in a couple months, as they live on the other side of the world. My thinking was it could be a good time for a memorial, but I now realize I can memorialize her without this.

EDIT: those asking why I won’t respect his wishes. I very much have for 6 years. This impending visit, however, has just ignited a lot of internal conflict but I get that it’s 100% his decision to make not mine.

EDIT: my strong belief shed want to be buried is because she purchased her parents plots and purchased additional ones for her, her sibling and their spouses. This is more than a hunch, but I’m mindful this is still not a legal will.