This won't be possible to do safely.
The Send bound is for transferring a value to another thread and a core principle of JavaScript is that it is single-threaded. That means no objects from JavaScript will implement Send.
Of course, you can probably work under the assumption that objects from your WebAssembly code will only ever stay on the main JavaScript thread, so it's fine to create a wrapper with an unsafe impl Send. However that unsafe assumption is now your responsibility to maintain.
struct Sendable<T>(pub T);
// Safety: WebAssembly will only ever run in a single-threaded context.
unsafe impl<T> Send for Sendable<T> {}
For example, if you decided you'd like to implement multi-threaded WebAssembly by spinning up web workers and using a common SharedArrayBuffer for their backing memory, then you'd need to go back and rethink whether your wrapper is still valid.