Committee transcripts (e.g. hearing transcripts, markup session transcripts) can be some of the most elusive Congressional documents.
Note that there is sometimes a significant lag-time between when a hearing or committee meeting is held and when official transcripts are published. In addition, each committee chooses whether to publish transcripts (or other committee materials) at all; not all materials are published or made available to the public. That said, third party publishers (see database list below) often provide unofficial transcripts of hearings that are available much sooner than official versions, and sometimes also transcripts of other committee meetings, like markup sessions. In addition, sometimes committee meetings or hearings are livestreamed on the committee's website and/or are broadcast on C-SPAN.
For very recent hearings you may find that transcripts are difficult to find. First, note that you may be able to obtain hearing materials from the committee website itself (House Committees / Senate Committees). The Federal News Service (available via Westlaw) also transcribes selected hearings and uploads them daily. Another source to check for recent hearing transcriptions is CQ Transcriptions on Nexis Uni (see note below).
You may also be able to find video recordings of hearings at C-SPAN.org (sometimes these have search-able closed captioning, though be aware that this captioning may contain spelling errors).
Miscellaneous documents from House Committees (bill versions, written witness statements, prints, etc.) can be found in the Committee Repository at docs.house.gov (click Committee Repository on the right, then Document Search at the top; run an initial search to get "Search Refinements" on the left, which allow for filtering by Committee, Meeting Type (Markup, Hearing, or Meeting), or Congress).
Note about Nexis Uni: If you are logged in to Lexis, Nexis Uni links may not work properly, and vice versa. Try accessing Nexis Uni in a separate browser from the one used to access Lexis. You can also try clearing your cache and cookies between uses of Lexis and Nexis Uni.