Missing a lot of information here that leaves way to much room for wild quessing based on no facts.
Our LLC
So I take it this is a multi-member LLC that reports taxes on IRS Form 1065?
sold a business in 2016
What kind of business? Another single member LLC? Multi-member LLC? S-Corp? C-Corp? Something else?
but we were still on the lease through February 2019.
Lease for what? If your LLC sold a business that your LLC owned, then explain the details of how "we" were on a lease for the sold business. This sounds like a "round robin" to me. But I'm sure it's not so you need to explain.
New owners filed bankruptcy in 2018 and we ended up paying about $45,000 in back lease payments and legal fees.
As I see it, the LLC you still own paid those expenses - not "we" pesonnally.
The LLC has wound down, so it will not be filing a return for 2019.
What LLC Wound down? The one that was sold? Or the one you still own? If the latter, did you file a "final" 1065 partnership return and issue "final" K-1's to all owners in a tax year prior to 2019?
How can I include these business expenses in my personal return?
Need more details before it can be determined if you even "can" claim anything on the personal return. If the owners of the LLC are not married to each other and filing a joint tax return, this *WILL* complicate matters quite significantly, and professional help would be highly recommended for dealing with this. Especially if your state taxes personal income since that would make this a double-whammy.
